Swift基础学习《The Swift Programming Language 中文版》前言部分代码示例

Posted 2020-10-03 CHM

  1 import UIKit
  2 
  3 var str = "Hello, playground"
  4 
  5 var myVariable = 42
  6 myVariable = 50
  7 let myConstant = 42
  8 
  9 let implicitInteger = 70
 10 let implicitDouble = 70.0
 11 let explicitDouble: Double = 70
 12 let explicitFloat: Float = 4
 13 
 14 let label = "The width is"
 15 let width = 94
 16 let widthLabel = label + String(width)
 17 
 18 let apples = 3
 19 let oranges = 5
 20 let appleSummary = "I have \(apples) apples."
 21 let fruitSummary = "I have \(apples + oranges) pieces of fruit."
 22 
 23 let float1 = 1.0
 24 let float2 = 3.0
 25 let floatString = "\(float1 + float2) CHM, Hi"
 26 
 27 var shoppingList = ["catfish", "water", "tulips", "blue paint"]
 28 shoppingList[1] = "bottle of water"
 29 
 30 var occupations = [
 31     "Malcolm": "Captain",
 32     "Kaylee": "Mechanic",
 33 ]
 34 occupations["Jayne"] = "public Relations"
 35 
 36 let emptyArray = [String]()
 37 let emptyDictionary = [String: Float]()
 38 shoppingList = []
 39 occupations = [:]
 40 
 41 let individualScores = [75, 43, 103, 87, 12]
 42 var teamScore = 0
 43 for score in individualScores {
 44     if score > 50 {
 45         teamScore += 3
 46     } else {
 47         teamScore += 1
 48     }
 49 }
 50 print(teamScore)
 51 
 52 var optionalString: String? = "Hello"
 53 print(optionalString == nil)
 54 
 55 var optionalName: String? = nil
 56 var greeting = "Hello!"
 57 
 58 if let name = optionalName {
 59     greeting = "Hello, \(name)"
 60 } else {
 61     greeting = "Hello, CHM"
 62 }
 63 
 64 let nickName: String? = nil
 65 let fullName: String = "John Appleseed"
 66 let informalGreeting = "Hi \(nickName ?? fullName)"
 67 
 68 let vegetable = "red pepper"
 69 switch vegetable {
 70 case "celery":
 71     print("Add some raisins and make ants on a log")
 72     case "cucumber", "watercress":
 73     print("That would make a good tea sandwich.")
 74 case let x where x.hasSuffix("pepper"):
 75     print("Is it a spicy \(x)?")
 76 default:
 77     print("Everything tastes good in soup.")
 78 }
 79 
 80 let interestingNumbers = [
 81     "Prime": [2, 3, 5, 7, 11, 13],
 82     "Fibonacci": [1, 1, 2, 3, 5, 8],
 83     "Square": [1, 4, 9, 16, 25],
 84 ]
 85 
 86 var largest = 0
 87 var largestKind = ""
 88 for (kind, numbers) in interestingNumbers {
 89     for number in numbers {
 90         if number > largest {
 91             largest = number
 92             largestKind = kind
 93         }
 94     }
 95 }
 96 
 97 print("\(largest, largestKind)")
 98 
 99 var n = 2
100 while n < 100 {
101     n = n * 2
102 }
103 print(n)
104 
105 var m = 2
106 repeat {
107     m = m * 2
108 } while m < 100
109 print(m)
110 
111 var total = 0
112 for i in 0..<4 {
113     total += i
114 }
115 print(total)
116 
117 func greet(person: String, day: String) -> String {
118     return "Hello \(person), today is \(day)."
119 }
120 greet(person: "Bob", day: "Thesday")
121 
122 func eat(name: String, food: String) -> String {
123     return "\(name) eat \(food) today."
124 }
125 
126 func greet(_ person: String, on day: String) -> String {
127     return "Hello \(person), today is \(day)."
128 }
129 greet("John", on: "Wednesday")
130 
131 func calculateStatistics(scores: [Int]) -> (min: Int, max: Int, sum: Int) {
132     var min = scores[0]
133     var max = scores[0]
134     var sum = 0
135     
136     for score in scores {
137         if score > max {
138             max = score
139         } else if score < min {
140             min = score
141         }
142         sum += score
143     }
144     
145     return(min, max, sum)
146 }
147 
148 let statistics = calculateStatistics(scores: [5, 3, 100, 3, 9])
149 print(statistics.sum)
150 print(statistics.2)
151 
152 func sumOf(numbers: Int...) -> Int {
153     var sum = 0
154     for number in numbers {
155         sum += number
156     }
157     return sum
158 }
159 
160 sumOf()
161 sumOf(numbers: 42, 597, 12)
162 
163 
164 func returnFifteen() -> Int {
165     var y = 0
166     func add() {
167         y += 5
168     }
169     add()
170     return y
171 }
172 returnFifteen()
173 
174 func makeIncrementer() -> ((Int)-> Int) {
175     func addOne(number: Int) -> Int {
176         return 1 + number
177     }
178     return addOne
179 }
180 
181 var increment = makeIncrementer()
182 increment(7)
183 
184 func hasAnyMatches(list: [Int], condition: (Int) -> Bool) -> Int {
185     for item in list {
186         if condition(item) {
187             return item
188         }
189     }
190     return 0
191 }
192 
193 func lessThanTen(number: Int) -> Bool {
194     return number < 10
195 }
196 
197 var numbers = [20, 19, 7, 12]
198 hasAnyMatches(list: numbers, condition: lessThanTen)
199 
200 numbers.map({
201     (number: Int) -> Int in
202     let result = 3 * number
203     return result
204 })
205 
206 let mappedNumbers = numbers.map({number in 3 * number})
207 print(mappedNumbers)
208 
209 //let sortedNumbers = numbers.sort{$0 > $1}
210 //print(sortedNumbers)
211 
212 class Shape {
213     var numberOfSides = 0
214     let addLetCode = 0
215     func simpleDescription() -> String {
216         return "A shape with \(numberOfSides) sides."
217     }
218     
219     func addLetCodeTest(par: Int) -> String {
220         return "a \(par) sides."
221     }
222 }
223 
224 var shape = Shape()
225 shape.numberOfSides = 7
226 var shapeDescription = shape.simpleDescription()
227 
228 class NamedShape {
229     var numberOfSides: Int = 0
230     var name: String
231     
232     init(name: String) {
233         self.name = name
234     }
235     
236     func simpleDescription() -> String {
237         return "A shape with \(numberOfSides) sides."
238     }
239 }
240 
241 class Square: NamedShape {
242     var sideLength: Double
243     
244     init(sideLength: Double, name: String) {
245         self.sideLength = sideLength
246         super.init(name: name)
247         numberOfSides = 4
248     }
249     
250     func area() -> Double {
251         return sideLength * sideLength
252     }
253     
254     override func simpleDescription() -> String {
255         return "A square with sides of length \(sideLength)."
256     }
257 }
258 
259 let test = Square(sideLength: 5.2, name: "my test square")
260 test.area()
261 test.simpleDescription()
262 
263 class EquilateralTriangle: NamedShape {
264     var sideLenth: Double = 0.0
265     
266     init(sideLength: Double, name: String) {
267         self.sideLenth = sideLength
268         super.init(name: name)
269         numberOfSides = 3
270     }
271     
272     var perimeter: Double {
273         get {
274             return 3.0 * sideLenth
275         }
276         set {
277             sideLenth = newValue / 3.0
278         }
279     }
280     
281     override func simpleDescription() -> String {
282         return "An equilateral triagle with side of length \(sideLenth)."
283     }
284 }
285 
286 var triangle = EquilateralTriangle(sideLength: 3.1, name: "a triangle")
287 print(triangle.perimeter)
288 triangle.perimeter = 9.9
289 print(triangle.sideLenth)
290 
291 class TriangleAndSquare {
292     var triangle: EquilateralTriangle {
293         willSet {
294             square.sideLength = newValue.sideLenth
295         }
296     }
297     
298     var square:Square {
299         willSet {
300             triangle.sideLenth = newValue.sideLength
301         }
302     }
303     
304     init(size: Double, name: String) {
305         square = Square(sideLength: size, name: name)
306         triangle = EquilateralTriangle(sideLength: size, name: name)
307     }
308 }
309 
310 var triangleAndSquare = TriangleAndSquare(size: 10, name: "another test shape")
311 print(triangleAndSquare.square.sideLength)
312 print(triangleAndSquare.triangle.sideLenth)
313 triangleAndSquare.square = Square(sideLength:50, name: "larger square")
314 print(triangleAndSquare.triangle.sideLenth)
315 
316 enum Rank: Int {
317     case Ace
318     case Two, Three, Four, Five, Six, Seven, Eight, Nine, Ten
319     case Jack, Queen, King
320     
321     func simpleDescription() -> String {
322         switch self {
323         case .Ace:
324             return "ace"
325         case .Jack:
326             return "jack"
327         case .Queen:
328             return "queen"
329         case .King:
330             return "king"
331         default:
332             return String(self.rawValue)
333         }
334     }
335     
336 }
337 
338 let ace = Rank.Ace
339 let aceRawValue = ace.rawValue
340 
341 if let convertedRank = Rank(rawValue: 0) {
342     let threeDescription = convertedRank.simpleDescription()
343 }
344 
345 enum Suit {
346     case Spades, Hearts, Diamonds, Clubs
347     
348     func simpleDescription() -> String {
349         switch self {
350         case .Spades:
351             return "spades"
352         case .Hearts:
353             return "hearts"
354         case .Diamonds:
355             return "diamonds"
356         case .Clubs:
357             return "clubs"
358         }
359     }
360     
361 }
362 
363 let hearts = Suit.Hearts
364 let heartsDescription = hearts.simpleDescription()
365 
366 enum ServerResponse {
367     case Result(String, String)
368     case Failure(String)
369 }
370 
371 let success = ServerResponse.Result("6:00 am", "8:09 pm")
372 let failure = ServerResponse.Failure("Out of cheese.")
373 
374 switch success {
375 case let .Result(sunrise, sunset):
376     let serverResponse = "Sunrise is at \(sunrise) and sunset is at \(sunset)."
377 case let .Failure(message):
378     print("Failure... \(message)")
379 }
380 
381 struct Card {
382     var rank: Rank
383     var suit: Suit
384     func simpleDescription() -> String {
385         return "The \(rank.simpleDescription()) of \(suit.simpleDescription())"
386     }
387 }
388 
389 let threeOfSpades = Card(rank: .Three, suit: .Spades)
390 let threeOfSpadesDescription = threeOfSpades.simpleDescription()
391 
392 protocol ExampleProtocol {
393     var simpleDescription: String { get }
394     mutating func adjust ()
395 }
396 
397 class SimpleClass: ExampleProtocol {
398     var simpleDescription: String = "A very simple class"
399     var anotherProperty: Int = 69105
400     func adjust() {
401         simpleDescription += "Now 100% adjusted."
402     }
403 }
404 
405 var a = SimpleClass()
406 a.adjust()
407 let aDescription = a.simpleDescription
408 
409 struct SimpleStructure: ExampleProtocol {
410     var simpleDescription: String = "A simple structure"
411     mutating func adjust() {
412         simpleDescription += "(adjusted)"
413     }
414 }
415 
416 var b = SimpleStructure()
417 b.adjust()
418 let bDescription = b.simpleDescription
419 
420 extension Int: ExampleProtocol {
421     var simpleDescription: String {
422         return "The number \(self)"
423     }
424     mutating func adjust() {
425         self += 42
426     }
427 }
428 
429 print(7.simpleDescription)
430 let protocolValue: ExampleProtocol = a
431 print(protocolValue.simpleDescription)
432 
433 enum PrinterError: Error {
434     case OutofPaper
435     case NoToner
436     case OnFire
437 }
438 
439 func send(job: Int, toPrinter printerName:String) throws -> String {
440     if printerName == "Never Has Toner" {
441         throw PrinterError.OnFire
442     }
443     return "Job sent"
444 }
445 
446 do {
447     let printerResponse = try send(job: 1040, toPrinter: "Never Has Toner")
448     print(printerResponse)
449 } catch {
450     print(error)
451 }
452 
453 do {
454     let printerResponse = try send(job: 1440, toPrinter: "Never Has Toner")
455     print(printerResponse)
456 } catch PrinterError.OnFire {
457     print("I‘ll just put this over here, with rest of the fire.")
458 } catch let printerError as PrinterError {
459     print("Printer error: \(printerError).")
460 } catch {
461     print(error)
462 }
463 
464 
465 let printerSuccess = try? send(job: 1884, toPrinter: "Mergenthaler")
466 let printerFailure = try? send(job: 1885, toPrinter: "Never Has Toner")
467 
468 
469 var fridgeIsOpen = false
470 let fridgeContent = ["milk", "eggs", "leftovers"]
471 
472 func fridgecontains (_ food: String) -> Bool {
473     fridgeIsOpen = true
474     defer {
475         fridgeIsOpen = false
476     }
477     
478     let result = fridgeContent.contains(food)
479     return result
480 }
481 
482 fridgecontains("milk")
483 print(fridgeIsOpen)
484 
485 func repeatItem<Item>(repeating item: Item, numberOfTimers: Int) -> [Item] {
486     var result = [Item]()
487     for _ in 0..<numberOfTimers {
488         result.append(item)
489     }
490     return result
491 }
492 repeatItem(repeating: "knock", numberOfTimers: 2)
493 
494 enum OptionalValue<Wrapped> {
495     case None
496     case Some(Wrapped)
497 }
498 
499 var possibleInteger: OptionalValue<Int> = .None
500 possibleInteger = .Some(100)
501 
502 func anyCommonElements<T: Sequence, U: Sequence>(_ lhs: T, _ rhs: U) -> Bool
503     where T.Iterator.Element: Equatable, T.Iterator.Element == U.Iterator.Element {
504         for lhsItem in lhs {
505             for rhsItem in rhs {
506                 if lhsItem == rhsItem {
507                     return true
508                 }
509             }
510         }
511         return false
512 }
513 
514 anyCommonElements([1, 2, 3], [3])